This invention relates to a syringe or the like used to extract or dispense pre-selected volumes of fluid through a needle during injections without dependency on eyesight. More particularly, the invention involves syringes utilized in medical applications which can provide a range of set dosages by simple one hand manipulation of the plunger against stop shoulders on the barrel of the syringe.
In time intensive hospital settings multiple dosages of constant volume must be routinely and quickly dispensed. To examine visual calibrations on current syringes for each dosage is time consuming and subject to error. Furthermore, during many injections, the visual attention of the operator and the use of one hand must often be necessarily directed to care and preparation of the patient. A problem therefore exists where selecting a proper dosage requires two hands and/or the visual attention of the operator. A problem also exists where a constant dosage syringe may need to be used to give non-standard dosages. Many syringes adapted to pre-selected dosages do not allow variable dosages without modification.
Often, the need also arises for individual or unskilled persons to give injections of certain dosages. For example, diabetics find it necessary to give themselves injections of insulin or other medications without medical assistance. Additionally, persons who have sight impediments have difficulty with syringes which are visually calibrated or which do not provide positive nonvisual manipulation to insure that only particular dosages are secured.
A number of devices have attempted to solve these problems. U.S. Pat. No. 4,117,728, discloses a pipette with shoulders for regulating movement of the pipette plunger. However, the stepped shoulders are close together and are only mounted on one side of the guide. This allows little sensitivity for manual, non-visual manipulation and does not provide the fail-safe manual, non-visual certainty necessary in most medical situations.
U.S. Pat. No. 2,792,834 provides an adjustable stop on the barrel of a syringe which appears complicated and costly to manufacture. U.S. Pat. No. 4,475,905, provides a track with numerous turns which must be traversed by a stop on the plunger, traversing these turns would appear to require time consuming and tedious attention by the operator. U.S. Pat. No. 4,267,846 provides a single stop within the barrel of the syringe which does not allow multiple fixed dosages or visual calibration. U.S. Pat. No. 4,084,730 provides a pipette with a complicated step mechanism for use with a detachable piston.
These and other patents provide plunger stop mechanisms which are complicated and expensive to manufacture, difficult to manipulate, and which require visual monitoring to assure that the correct dosage is used. The instant invention solves these problems with a simple stop system allowing multiple fixed dosages to be delivered with speed, fail-safe accuracy, and without visual aid.
It is therefore an object of the invention to provide fail-safe manual manipulation for determination of fixed dosages without the need for visual aid yet provide variable visual calibration when necessary. Another object of the invention is to provide a simple, low cost, disposable syringe. A further object of the invention is to provide a syringe with the above characteristics which can be used by blind and unskilled persons.